Scientists have successfully constructed the first complete energy spectrum of solar high-energy protons observed during an eruptive solar event occurring in Martian space. This remarkable achievement deepens our understanding of the radiation environment surrounding Mars, shedding light on critical aspects of space weather phenomena and their implications for future exploration missions.
Introduction
Solar energetic particle (SEP) events are induced by solar eruptions and represent one of the most destructive space weather phenomena. During these events, there can be a sudden increase in the flux of high-energy charged particles in space, significantly affecting spacecraft operations and posing serious risks to astronauts. Unlike Earth, Mars does not possess a protective magnetic field, and its atmosphere is notably thin. Consequently, its surface is highly vulnerable to high-energy particles and secondary particles emitted during these solar events. Therefore, studying the impact of SEP events on Mars is invaluable for assessing radiation protection in future Mars exploration missions.
Background of the Study
The study involved collaboration among several leading research institutions, including the University of Science and Technology of China, the Institute of Modern Physics of the Chinese Academy of Sciences (CAS), the Lanzhou Institute of Physics, and the University of Kiel in Germany. The findings were published in Geophysical Research Letters as a cover article.
In November 2021, China's Tianwen-1 orbiter entered its science mission orbit around Mars. Equipped with a Mars Energy Particle Analyzer (MEPA), it began measuring the particle flux in the Martian environment. The MEPA features an extensive energy measuring range of 2–100 MeV, which significantly enhances its capability to monitor high-energy protons in Martian space, providing critical data for the researchers involved in this study.
The February 2022 SEP Event
On February 15, 2022, the MEPA recorded an SEP event characterized by exceptionally high intensity and energy levels. This event was notable as it was simultaneously detected by several additional instruments, including the European Space Agency's Trace Gas Orbiter (TGO), NASA's Mars Atmosphere and Volatile Evolution Orbiter (MAVEN), and the Curiosity rover on the Martian surface. This represents the first instance where an SEP event has been observed by such a diverse array of radiation detectors at Mars.
Data Collection and Methodology
For this study, the researchers utilized data from various detectors to construct the proton energy spectra comprehensively. The low- and medium-energy proton spectra were furnished by the Tianwen-1 orbiter and MAVEN, while observations from the Curiosity rover were combined with simulations of particle transport in the Martian atmosphere to derive high-energy proton flux measurements. By fitting the observed and derived fluxes across differing energy ranges, researchers were able to successfully construct a complete proton energy spectrum for the SEP event, encompassing energies spanning from 1 to 1000 MeV.
| Energy Range (MeV) | Source of Data | Comments |
|---|---|---|
| 2 - 100 | Tianwen-1 MEPA | Low and medium energy measurements |
| 100 - 1000 | Curiosity rover with simulations | Determined high energy flux through modeling |
Impact and Validation of the Findings
The researchers proceeded to calculate the radiation dose associated with this SEP event within the context of Martian orbit and on the Martian surface, discovering that their findings were consistent with actual dose measurements observed. This correlation validates both the reliability of the data gathered by the Tianwen-1 MEPA and the efficacy of the Martian radiation transport model developed by the researchers.
This investigation serves as a reference point for future studies concerning similar space weather phenomena while underscoring the need for ongoing, coordinated radiation monitoring efforts on Mars. As humanity moves toward potential colonization of Mars, understanding the risks associated with solar events is essential to ensuring the safety of astronauts and the equipment they depend on in these extreme environments.
Conclusion
The successful construction of the first complete proton energy spectrum for an SEP event in Martian space is a significant advancement in planetary science and space exploration. By employing sophisticated monitoring techniques and leveraging data from multiple sources, researchers have elucidated essential information about the radiation environment that influences both past and future robotic and human missions to Mars.
References
[1] Jian Zhang et al, The 2022 February 15 Solar Energetic Particle Event at Mars: A Synergistic Study Combining Multiple Radiation Detectors on the Surface and in Orbit of Mars With Models, Geophysical Research Letters (2024). DOI: 10.1029/2024GL111775
[2] Chinese Academy of Sciences, Tianwen-1 rover and its findings (2021). Available online: CAS
[3] NASA, The Mars Atmosphere and Volatile Evolution Mission overview. Available online: NASA MAVEN
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